/Engine/Source/Runtime/GeometryCore/Public/DynamicMesh/MeshNormals.h
the computed overlay normal at an element of the overlay (ie based on normals of triangles connected to this element)
static FVector3d ComputeOverlayNormal ( const [FDynamicMesh3](API\Runtime\GeometryCore\DynamicMesh\FDynamicMesh3) & Mesh, const [FDynamicMeshNormalOverlay](API\Runtime\GeometryCore\DynamicMesh\FDynamicMeshNormalOverlay) * NormalOverlay, int ElemIdx, bool bWeightByArea, bool bWeightByAngle )